File extensions – definition and basic information


File extensions are the integral parts of the files that are on each computer. Often, when working on a computer, we encounter a wide range of files, such as docx, ppt, part, mp3 or rmvb. We realize that they are there – but we often do not know what they are for on our computer.

File extension, also known as the filename extension is a suffix added to the name of a computer file, usually consisting of a number of characters placed after the last dot in the filename, which gives us information about its coding. In other words a file extension is a file format. It allows the operating system (e.g. Windows) to recognize what program it should try to open the file.

In the table below you will find a random selection of popular file extensions.


File extension The full name of the file Category

APP file extension

Mac OS X Application

Executable Files

ASP file extension

Active Server Page

Web Files

AVI file extension

Audio Video Interleave File

Video Files

CFG file extension

Configuration File

Settings Files

CUE file extension

Cue Sheet File

Disk Image Files

DBF file extension

Database File

Database Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

FLV file extension

Flash Video File

Video Files

GAM file extension

Saved Game File

Game Files

INI file extension

Windows Initialization File

Settings Files

JAR file extension

Java Archive File

Executable Files

KEY file extension

Keynote Presentation

Data Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

ROM file extension

N64 Game ROM File

Game Files

3GP file extension

3GPP Multimedia File

Video Files